Admin theme broke. How to get it back? (3 posts)

Maybe someone can help with this.
Our website is functioning perfectly. Everything's in place.
However, upon entering the Admin dashboard, I noticed everything looked out of place. The Admin theme looked broken, all the gifs and icons were still there, but the theme was reduced to a minimalistic-mid-90's-html-like-page.

I've tried deactivating the plug-ins one by one and then re-logging in, but so far that hasn't worked.

Any ideas on how I can get the Admin theme back?
I'm not even able to do automatic downloads/updates this way... the page gets stuck when trying to upgrade whatever plugin/package there's available, and doesn't complete the downloads.